/Engine/Source/Runtime/RHI/Public/RHIFeatureLevel.h
The RHI's feature level indicates what level of support can be relied upon. Note: these are named after graphics API's like ES3 but a feature level can be used with a different API (eg ERHIFeatureLevel::ES3.1 on D3D11) As long as the graphics API supports all the features of the feature level (eg noERHIFeatureLevel::SM5on OpenGL ES3.1)
namespace ERHIFeatureLevel { enum Type { ES2_REMOVED, ES3_1, SM4_REMOVED, SM5, SM6, Num, } }